The present invention relates to a card-like medium and a PC card for, upon insertion into a slot provided in the body of an information processing apparatus, performing data communications with the information processing apparatus via a bus.
Conventionally, there have been proposed PC cards serving for expanding the potential of information processing apparatuses such as personal computers. A PC card, when inserted into an exclusive slot provided in the body of an information processing apparatus, is connected to the information processing apparatus with buses (data bus, address bus, control bus) or the like. Some PC cards play a role as a recording medium, and others as an interface with externally connected equipment. Only by exchanging the PC cards to be inserted into the slot, the user is allowed to make use of the functions of the inserted PC card in the information processing apparatus, thus enabled to extend and change the functions of the information processing apparatus with simplicity and ease.
However, with the conventional 16-bit system, in which an information processing apparatus and a PC card are connected to each other with a 16-bit wide data bus, only a maximum of 16-bit data can be transferred in one cycle of data transfer. As a result, there has been a problem that a long time would be taken from start to completion of data transfer in the processing of high volume of transfer data. This being the case, the CardBus system, in which an information processing apparatus and a PC card are connected to each other with a 32-bit wide data bus, has been proposed as a PC card standard. An information processing apparatus compatible with this system (CardBus-compatible information processing apparatus) has a function of discriminating whether or not a PC card inserted into the slot is CardBus compatible, where if the PC card is CardBus compatible, the apparatus connects the PC card with a 32-bit wide data bus (connection in the CardBus system); if the PC card is 16-bit compatible other than CardBus compatible, the apparatus connects the PC card with a 16-bit wide data bus (connection in the 16-bit system), thus the information processing apparatus being enabled to use both CardBus-compatible PC cards and 16-bit-compatible PC cards.
However, CardBus-compatible PC cards have been so designed as to be usable only in CardBus-compatible information processing apparatuses, and not in CardBus-incompatible, 16-bit-compatible information processing apparatuses. Therefore, in order to enable the use of a PC card in both CardBus-compatible information processing apparatuses and 16-bit-compatible information processing apparatuses, it has been inevitable to use a 16-bit-compatible PC card. In this case, a 16-bit-compatible PC card would be used in a CardBus-compatible information processing apparatus, resulting in a problem that the functions of the CardBus-compatible information processing apparatus could not be fully exploited.
Even among CardBus-compatible information processing apparatuses, some operating systems (OS) have no software for CardBus-compatible socket services or the like, where while the information processing apparatus is running on such an OS, CardBus-compatible PC cards are unusable. Also, with a CardBus-compatible PC card used in a CardBus-compatible information processing apparatus, there are some cases where the information processing apparatus proper or its peripheral equipment become unstable in operation depending on the environment in which the PC card is used. Further, among CardBus-compatible information processing apparatuses having two or more slots for insertion of a PC card, there are some apparatuses in which two CardBus-compatible PC cards, when inserted into the apparatus, become unusable in terms of the specifications of the information processing apparatus (where a CardBus-compatible PC card and a 16-bit-compatible PC card, when inserted into the apparatus, are usable). From these and other reasons, there has been a demand for a PC card that can be operated in either the 16-bit mode or the CardBus mode optionally depending on the use environment. Also, whereas it is conceivable that a system for standards of longer data bus width emerge in the future to substitute for the CardBus system, problems similar to those described above may arise also in such a case. Therefore, under the existing circumstances, there is a general demand for the emergence of a PC card or a card-like medium that can be operated in a plurality of modes which are different from one another in data bus width.
Accordingly, it is an object of the present invention to provide a card-like medium and a PC card which can be changed over between two kinds of operational modes that are different from each other in the width of the data bus by which data communications with information processing apparatuses are performed, so that the card-like medium and the PC card can be operated properly in accordance with the use environment.
In order to achieve the above object, according to the present invention, there is provided a card-like medium which, when inserted into a slot provided in an information processing apparatus proper, is connected to the information processing apparatus proper, the card-like medium comprising:
a control section for controlling operation in a first operational mode in which data communications with the information processing apparatus proper are carried out with a data bus having a first bit width, and operation in a second operational mode in which data communications with the information processing apparatus proper are carried out with a data bus having a second bit width; and
selection means for selectively changing over between the first operational mode and the second operational mode.
The card-like medium of this constitution is inserted into a slot provided in the body of the information processing apparatus, and connected to the information processing apparatus. The selection means serves for changing over the operational mode in which the card-like medium performs data communications with the information processing apparatus by means of the data bus having the first bit width or the data bus having the second bit width. Therefore, the card-like medium can be selectively changed over in operational mode depending on the functions of the information processing apparatus proper to which the card-like medium is connected. Thus, the card-like medium is enabled to make full use of the functions of the information processing apparatus proper.
When the selection means is a hard switch which is changed over artificially, the user is enabled to intentionally select an operational mode, so that the card-like medium can properly be operated in accordance with the use environment.
When the selection means changes over the operational mode depending on state of a specific signal inputted from the information processing apparatus proper, the card-like medium can make the selection means automatically select the first operational mode when the card-like medium is inserted into an information processing apparatus compatible with the first operational mode and select the second operational mode when the card-like medium is inserted into an information processing apparatus compatible with the second operational mode.
The card-like medium further comprises a hard switch for changing over a selection as to whether the operational mode is fixed to the first operational mode regardless of the state of the specific signal.
With this arrangement, for example, when the card-like medium is inserted into an information processing apparatus compatible with both the first operational mode and the second operational mode, the card-like medium can be operated with the operational mode fixed to the first operational mode.
With an arrangement that the hard switch is provided so as to be located inside the slot when the card-like medium is connected to the information processing apparatus, the hard switch located inside the slot is disabled from changing-over operation when the card-like medium and the information processing apparatus are connected to each other. Therefore, while data communications between the card-like medium and the information processing apparatus are going on, the card-like medium can be prevented from being changed over in operational mode by a user""s misoperation of the hard switch. This also prevents occurrence of problems such as malfunction due to a changeover of the operational mode during the operation and damage of the card-like medium and the information processing apparatus.
With an arrangement that the card-like medium further comprises a constant-voltage power supply circuit which is fed with power supply from the information processing apparatus proper and supplies a generally constant-voltage operating power to individual sections of the card-like medium, the individual sections of the card-like medium can be free from any damage due to application of an overvoltage even when the voltage of the power supplied from the information processing apparatus proper differs depending on the information processing apparatus to which the card-like medium is connected.
Further, by applying the present invention to a PC card, where the first operational mode is a mode in which data communications based on the 16-bit system are carried out (16-bit mode) and the second operational mode is a mode in which data communications based on the CardBus system are carried out (CardBus mode), a PC card which can be operated in an optimal mode in accordance with the use environment can be obtained.